Countercurkent sltjbb



Patented Mar. 17, 1953 UNITED STATES PATENT GF'FICE to Texaco Dexreloprnen'tH Corporation,

New

York, yN.Y., a' corporation of Delawarev Application rime 24, 1950, seria1.o.'1`70,090

l-l-Claims.

This invention relates to a process for `effecting" complex formation between' complexin'g agents such as'urea and complex-forming consttuents of an'organic mixture. More partic= ularly, this invention discloses a continuous process for separating normal aliphatic constituents from an'organic mixture; u Y

In" accordance with the process of' this in; vention, removal' of complexef'orming' constituents 'from an organic mixture's eeoted by a continuous process involving counter current contact'of an organic mixture 'with a slurry' of complexing'agent and solid carrierv in a'polar solvent. The slurry of complexing agent and solid carrier in a polar 'solvent is introduced into 'the upper' 'portion of the contacting tower While the organic mixture is introduced'into the loWer 'section thereof` Solid' complex' comprising complexing agent and complex-forming 'constituents of said organic mixture' is formed dur'- ingthe 'counterc'urrent contact, is' entrained 'in the slurry and is removed from 'thepOntacti-"ng zone therewith. Water, alcohols'such'as'methyL ethyl and butyl alcohols, ketones such'V a'sace'# tOne,A methyl ethyl ketone, and methyl isobtyl ketone, and mixtures of such' polar solvents are employed to4 form' the' slurry of Complexing agent and solid carrier. Complex'de'c'omp'osit'ion is effected by heating the slurry comprising" com'- plex, complexng agent and solici'V carrier suspended in' poiar'soiv'e'nt'to a temperature alcove about 140ci F. in' a 'separate vessel andY the liber; ated complex'formi'ng' constituents "are separated from the slur'r'y' at elevated temperature', where'- aft'er the slur'ry'ds -recycled to contact further quantities of organic mixture.

It' has 'recently been discovered 'that urea 'and thiourea form' solid complexes With 'certain' types of Aorganic compounds. The 'class 'of' compounds which complex with urea comprises normal' ali'- phatic hydrocarbons containing at least six carbon' atoms', terminal-substituted normal aliphatic hydrocarbons containing" at least six' carbon atoms, such. as n'dec'anol and nedodecylbenz'ene and some methyl-substituted n-alipha'tic hydro'- carb'ons'.' Thi'oure'a'forms' solid complexes' 'with some"branehed .chain hydrocarbons'- and' some x'1aphth`er'1'es`;` triptane', 2,3dimetl'iylloutanev are examples Vof branched chain hydrocarbonsv that complex 'with thioureaj cyclopenta'ne and cyclohexane are examples of naphthenes which complex'with thiouera'. The discovery of the corn'- pleit-formingV ability of ureawan'd thiourea provides va very useful 'tool in' the resolution of or'- glnc "mixtures Such aS Y petroleum" fractions.

2. Urea" complexing is`V particularlyv useful'in tl-ie isolationV of' specific compoundsl andin tlc-ere-y moval of undesirable-components from petroleum fractions. Devvaxing'of4 petroleumsfractions such a's gas oils and lubricating oils to produce A10WY Wax content products-illustrates lthe use of urea cornplexingv to freea petroleum fraction'of u'n-y desirable constituents. The" InainA commercial usefulness ofurea'complexing at-"thel present time lies in' thedev'vaxingof gas oils and' lubricating' oil fractions; lovv'pour'diesel fuel is in demand as'a jet-fuel and' for cold Weatherop'ration of diesel engines; refrigerator oils vcharacterized by 10W" pour-'and' f-re'o'n haze testsare required` in air conditioning and refrigeration equipment.

Various procedures have'v` been propos'edfor effecting complex 'formationl between complexing agents such' asurea land complex`formin`gJeon-v stituents ofA organic mixtures. It has-'been proposed that complex formation bey effect'edlby contacting 'an organic'ymixfture Witha saturated or super-saturated solution ofureahin a polar solvent such as aliphatic alcohols,- aliphatic ketones, Water, etc. Complexfrmation-sf-also effectedv `by contacting anl organicy mixture'i-With a' slurry ofcomplexing-'agent ina polar solvent.

In addition, complex formation is effected-by contacting an"org'anicmixturewith a yiixedbed Of'ure'a wherein thefl'irea is'` ell'fiplo'y'edV4 lic'rlYi junction' with a particular' solid-Wlfiichs raclvantageously an;adsorbent".l In theseffVarious techniques for effecting complex formation; the presence of a polar compound such` as Water',-f an aliphatic alcohol, or an aliphatic ketone`` ex'- pedites complex'formation. However'; all ofthe aforedescrioed"techniques involve vthe use-o-flltration or decant'ationoperationsto separate the complex from thef'-organic-irnixture'.-

This invention' providesra" processwheeby complex formation is eect'e'cl by a-continous operation which `is similar'*tov al liquid phase op'- erationI inv that it avoids the' use o'f flltrationy or decantation techniques 'for separating'the'coplex.A Continuous countercurre'nt contact'- of an organic mixture with a-v slurry of` complexing agent vandv` solid carrieriin Va' "polar solvent-results in complexn formation' and entrainmenthof the complex in the'slurry phase which is* readily separated' from the Aorganic mixture. In essence, therefore, the process is essentially'- a liquid phase operation and is endowed.: with! all the advantages attendant uponliquid-l'iqiii eration. Consequently," process Iof'fthis in"- 'ven'tion' is'a substantialV step forward inv eox- 3 mercializing processes involving complex formation.

The distinction between the subject application and prior art processes is that incorporation of the solid carrier, which is preferably an adsorbent, in the slurry permits the use of a countercurrent system which is a facsimile of countercurrent liquid-liquid contact. Apparently the presence of the carrier in slurry results in substantial entrainment of the formed complex in the slurry phase. In previously practiced slurry systems for complex formation in which the solid carrier was not an integral part of the slurry, the formed complex positioned itself at the interface of the organic mixture and slurry phases. The presence of the complex at the interface prevented simple separation of the complex from the organic mixture. However, in the process of this invention the complex is entrained in the slurry phase with the result that separation of the organic mixture from the complex is readily effected. Another advantage resulting from the incorporation of a solid carrier as an integral component of the slurry phase is that a sharper division results between the organic mixture and slurry phases. The function of the carrier is apparently two-fold; it entrains a complex substantially in the slurry phase and makes possible a sharper separation between the organic mixture and the slurry.

The preferred modification of the invention wherein the solid carrier component of the slurry is an adsorbent is accompanied by a further advantage. The presence of an adsorbent in the slurry results in a partial refining of the treated organic mixture. This is particularly useful when a lubricating oil fraction is treated in accordance with the process of this invention. Colorforming bodies and impurities which result in poor emulsifying properties are removed together with waxy constituents from a lubricating oil fraction employing a slurry comprising urea and adsorbent in a polar solvent.

While adsorbents such as silica gel, Filter Cel, alumina are the preferred solid carriers used in making the slurry, granular non-adsorbent solids such as sand may also be used to prepare the slurry.

The slurry employed in the process of this invention ordinarily comprises a 50-50 mixture of complexing agent and carrier in polar solvent. However, the complexing agent carrier weight ratio can vary from 3 to 1 to l to 3. The polar solvent is at least equal in weight to the weight of the solid portion of the slurry. Advantageously, the solvent comprises 2 to 5 weights of solvent per weight of solid fraction consisting of complexing agent plus carrier.

The preferred polar solvent for the process of this invention is water since best separation of organic mixture and slurry is realized therewith. It is advisable to add 5 to 10 per cent solubilizing agent, such as ethyl or propyl alcohol, methyl ethyl ketone and methyl isobutyl ketone, to the perferred water solvent in order to effect more rapid complex formation. The presence of 5 to l0 per cent solubilizing agent in the water used as the slurry medium enhances complex formation by providing a medium wherein the organic mixture and the urea can come into intimate molecular contact without having an adverse effect on the sharp separation of slurry from the organic mixture. Another advantage of employing water as the slurry medium is that decomposition of the complex and separation of the complex-forming components are readily effected therewith; the complex is decomposed by heating the aqueous slurry to a temperature above about F. whereby there is formed a 2-phase system, one phase comprising complex-forming constitutents and the other phase comprising aqueous slurry of urea. The layer -of complex-forming constituents is readily separated from the aqeuous slurry,

The process of the invention is also applicable with other polar solvents, such as methanol, ethanol, propanol, acetone, methyl ethyl ketone. The use of organic polar solvents of high molecular weight such as butanol and methyl ethyl ketone as slurry mediums necessitates the use of an extraction technique to separate the complex-forming constituents from the decomposition mixture.

The countercurrent contact process of this invention is effected at much higher capacity than previously disclosed fixed-bed techniques for effecting removal of complex-forming constituents from an organic mixture. Employing the process of this invention, l0 to 30 volumes of organic mixture may be contacted with one volume of slurry per hour. In general, a contact time of approximately 2 to 5 minutes should be employed in the countercurrent process of this invention.

The contact between the organic mixture and the slurry of urea and adsorbent in the polar solvent must be effected at temperatures below about 140 F. Advantageously, however, temperatures between E10 and 120 F. are employed in the process. When the object of the invention is to remove low molecular weight complexforming constituents, such as hexane, heptane and octane from a gasoline fraction, temperatures between 0 and 50 F. must be employed. In general, however, room temperature has been found to be effective for the removal of C10 and higher normal aliphatic hydrocarbons from. organic mixtures.

Apparently the process does not possess critical pressure limitations. Accordingly, atmospheric pressure is ordinarily employed although there appears to be no objection to the use of sub-atmospheric or super-atmospheric pressures if the use of these pressures is dictated by other considerations.

In some instances it is desirable to recover the complex-forming constituents removed from the organic mixture because of the premium price such products attract. In most instances, however, decomposition of the complex is recommended so that a continuous process is feasible wherein aqueous slurry from which the complex-forming constituents have been removed is recycled to contact further quantities of organic mixture. In either' event decomposition of the complex is effected by heating the slurry removed from the contacting zone and containing entrained complex to a temperature above 140 F. Such treatment decomposes the complex into complex-forming constituents and urea. As has been indicated previously, when water or water containing up to about 10 per cent solutizer is employed as the slurry solvent, the complexforming constituents are readily separated from the aqueous slurry in two-layer systems formed on decomposition of the complex. Moreover, any complex-forming constituent which is not removed from the slurry recombines with the urea upon cooling of the slurry to form complexes whose presence is benecial in expediting the formation of complex on contact of recycled urea with organic mixture. When the polar solvent employed as the urea medium contains low hydrocarbon solubility, complex recycle is very advantageous as is disclosed in a co-pending application, Serial No. 143,838, entitled Process for Forming Urea Complexes, led February 1l, 1950, in the names of George B. Arnold, James K. Truitt and Howard V. Hess.

When more hydrocarbon-like solvents such as butanol and methyl isobutyl ketone are employed as the slurry solvent, decomposition of the complex by heating the slurry to a temperature above 140 F. does not result in as clear-cut a separation between the complex-forming constituents and the slurry. Accordingly, it'is sometimes necessary to extract the bulk of the complexforming constituents from the slurry with solvents such as benzene or toluene which do not form complexes with urea. As has been indicated in discussing decomposition of an aqeuous slurry, it is not necessary to remove all of the complex-forming constituents from the decomposed solution since the presence of recycled complex which is formed on cooling the slurry is advantageous in the contacting zone. With solvents such as methanol and ethanol, sufficient separation between the complex-forming constituents and the slurry is realized on complex decomposition that it is not necessary to resort to extraction to separate complex-forming constituents.

In the accompanying gure there is diagrammatically illustrated the preferred modification of this invention involving removal of complexforming constituents from an organic mixture such as lubricating oil by Countercurrent contact with an aqueous slurry of urea and solid adsorbent such as Porocel.

A lubricating oil fraction having a pour of about 50 F. and Freon haze test of 20 F. and a Lovi. color of 85 in the 6" cell is introduced through a feed pipe l into the lower portion of a contacting tower 2. In the contacting tower 2 the lubricating oil fraction is contacted countercurrently with an aqueous slurry of urea and Porocel comprising 5 weights of water per weight of solid fraction consisting of a 50-50 urea- Porocel mixture. This aqueous slurry is introduced into the upper portion of the tower 2 through a pipe 3. Countercurrent contact of the lubricating oil fraction with the aqueous slurry of urea and adsorbent at room temperature results in color improvement of the lubricating oil fraction and removal of normal aliphatic waxes therefrom which entered into complex formation with the urea portion of the slurry. The formed complex was entrained in the slurry because of the presence of the adsorbent therein. In addition, separation of the slurry from the organic mixture is enhanced by the presence of adsorbent in the aqueous slurry.

Dewaxed oil substantially free of complexforming constituents is withdrawn from the top of the contacting tower 2 through a pipe 5 through which it is introduced into a wash tower 6 wherein it is contacted with an alcohol-water solution for removal of entrained urea and complex therefrom. The alcohol-water wash is introduced into the wash tower 6 through a pipe 'l and is removed from the upper portion thereof through a pipe 8. Dewaxed oil containing some entrained alcohol and water but substantially free of wax and residual urea and complex is withdrawn from the wash tower through a pipe I2 and is therethrough introduced into a stripper I3 wherein alcohol and waterv are re,- moved from the oil. The entrained alcoholwater are obtained overhead from separator I3 through I4. Finished oil which has a Lovi. 6" color of 55, a pour of 80 F. and a Freon haze test of is withdrawn from the stripper through a pipe l5. The color improvement in the oil indicates -that a partial refining has been effected by the Countercurrent contact withl the aqueous slurry 'of urea and adsorbent, and the substantial improvement in pour and Freon haze indicate that a substantial portion of the vcomplexforming constituents, namely paralinic waxes, have been removed from the lubricating oil by the Countercurrent contact with the slurry. This finished oil is an excellent refrigerator oil.

From the bottom portion of the contacting tower 2 through a pipe 20 there is removed an aqueous slurry which contains urea adsorbent and entrained complex. This slurry is introduced into a vessel 2l provided with heat exchange means 22. In the vessel 2| the aqueous slurry containing entrained complex is heated to a temperature above about 140 F. whereby the complex decomposes into urea and liquefied paraffin waxes. As a result of the decomposition procedure there is formed two phases, the upper phase comprising liquefied wax and the lower phase comprising aqueous slurry of urea and adsorbent. The liquefied waxy layer is withdrawn from the vessel 2| through a pipe 24. On solidication these waxes form a high melting point wax which is useful in the packaging industry to form water-tight containers.

From the lower portion of the Vessel 2l there is withdrawn an aqueous slurry of urea and adsorbent at an elevated temperature. This slurry is passed along the pipe 25 to a heat exchanger 26 where it is cooled to a temperature in the range of '70 to 120 F. As a result of this cooling procedure there is formed some complex between urea and residual entrained paraffin waxes. The presence of' these parain waxes in the recycle aqueous urea promotes complex formation in the contacting tower 2. The ycooled aqueous slurry is recycled to the contacting tower 2 through a pipe 21.

Make-up urea and adsorbent can be introduced into the slurry from Atime to time from the hop-per 30 which connects with the feed line 3 through a pipe 3|.

The above-outlined procedure discloses a preferred method for removing complex-forming constituents Afrom organic mixtures in accordance with the process of this invention. It will be realized that other feed stocks and other slurry solvents and other solid carriers can be employed in the foregoing description of the invention.

It is Well to note that it is advisable to reduce the viscosity of very viscous lubricating oils when they are employed as the organic mixture from which complex-forming constituents are to be removed in accordance -with the process of this invention. In order to effect good contact between the slurry and the feed oil, it is advisable that the viscosity of the organic mixture be less than Saybolt Univ. Viscosity at 100 F. When the viscosity is less than the specified figure, ready separation is effected between the organic mixture and slurry of urea adsorbent and entrained complex.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof and, therefore. only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A process for removing from an organic mixture constituents which form complexes with a urea-type complexing agent which comprises subjecting said organic mixture in a contacting zone to countercurrent contact with a polar solvent slurry comprising 25 to '75 per cent solid particulate adsorbent and 75 to 25 per cent complexing agent selected from the group consisting of urea and thiourea, forming complexes between said complex-forming constituents and said complexing agent during said contact, entraining said complex in said slurry and separately removing froz-.i seid contacting zone said complexcontaining slurry and said organic mixture substantially free from said complex-forming ccnstituents.

2. A process for removing from an organic mixture constituents which form complexes with urea which comprises subjecting said lorganic mixture in a contacting zone to countercurrent contact with a polar solvent slurry comprising 25 to 75 per cent solid particulate adsorbent and 75 to 25 per cent urea, forming complexes between said urea and said complex-forming constituents during said contact, entraining said complex in said slurry and separately removing from said contacting zone said complex-containing slurry and said organic mixture substantially free from said complex-forming constituents.

3. A process according to claim 2 in which contact of organic mixture with polar solvent slurry is eiected at a temperature below 140 F.

4. A process according to claim 2 in which water is the polar solvent.

5. A process according to claim 2 in which the polar solvent content of said slurry is approximately 2 to 5 times the yweight of adsorbent plus urea.

6. A process according to yclaim 2 in which a contact time of about 2 to 5 minutes is employed.

'7. A process for removing complex-forming constituents which are mainly n-parainic hydrocarbons from a hydrocarbon mixture which comprises subjecting said hydrocarbon mixture in a contacting zone to countercurrent, contact at a temperature less than 140 F. with a polar solvent slurry comprising 25 to '75 per cent solid particulate adsorbent and 75 to 25 per cent urea, forming complexes between said urea and said complex-forming constituents during said contact, entraining said complex in said slurry, and separately removing from said contact zone said complex-containing slurry and said hydrocarbon mixture substantially free of said complexforming constituents.

8. A process for removing from a hydrocarbon mixture complex-forming constituents which are mainly n-parainic hydrocarbons which Icomprises subjecting said hydrocarbon mixture in a contacting zone to countercurrent contact at a temperature below 140 F. with a polar solvent slurry comprising 25 to 75 per cent solid particulate adsorbent and 75 to 25 per cent urea, forming -complexes between said urea and said complex-forming constituents during said contact, entraining said complex in said slurry, separately removing from said contacting zone said complex-containing slurry and said hydrocarbon mixture substantially free from complexforming constituents, heating said slurry to a temperature above 140 F'. whereby said complex is decomposed into complex-forming constituents and urea, separating said liberated complexforming constituents and recycling residual slurry to contact further quantities of said hydrocarbon mixture.

9. A process according to claim 8 in which water is the polar solvent.

10. A process according to claim 8 in which a contact time of about 2 to 5 minutes is employed for countercurrent contact of slurry and hydrocarbon mixture.

11. A process according to claim 8 in which polar solvent content of said slurry is approximately 2 to 5 times the weight of adsorbent plus urea.

HOWARD H. GROSS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,336,333y Morris Oct. 9, 1945 2,386,358 Schulze et al. Oct. 9, 1945 2,499,820 Fetterly Mar. '7, 1950 OTHER REFERENCES Bataafsche, Australian application 17,339/47, received November 2, 1949. 

1. A PROCESS FOR REMOVING FROM AN ORGANIC MIXTURE CONSTITUENTS WHICH FROM COMPLEXES WITH A UREA-TYPE COMPLEXING AGENT WHICH COMPRISES SUBJECTING SAID ORGANIC MIXTURE IN A CONTACTING ZONE TO COUNTERCURRENT CONTACT WITH A POLAR SOLVENT SLURRY COMPRISING 25 TO 75 PER CENT SOLID PARTICULATE ADSORBENT AND 75 TO 25 PER CENT COMPLEXING AGENT SELECTED FROM THE GROUP CONSISTING OF UREA AND THIOUREA, FORMING COMPLEXES BETWEEN SAID COMPLEX-FORMING CONSTITUENTS AND SAID COMPLEXING AGENT DURING SAID CONTACT, ENTRAINING SAID COMPLEX IN SAID SLURRY AND SEPARATELY REMOVING FROM SAID CONTACTING ZONE SAID COMPLEXCONTAINING SLURRY AND SAID ORGANIC MIXTURE SUBSTANTIALLY FREE FROM SAID COMPLEX-FORMING CONSTITUENTS. 